The Ultimate Mental Math Trick: How to Know the Day for Any Date
Can you tell the day of any date without a calendar handy? Is that really possible?
It is actually a simple skill that anyone can learn. It is also very practical since you can always consider your availability for an activity or an event or you simply need to know someone’s birthday. All it takes is a little practice, then you can quickly and easily tell the day of the week for virtually any date in history or in the future.
Here is the secret
You may need to memorize a few codes to learn this trick, but they are very easy to remember.
First, we assign a code number to every day of the week.
Monday – 1
Tuesday – 2
Wednesday – 3
Thursday – 4
Friday – 5
Saturday – 6
Sunday – 7 or 0
Second, we assign a code number for each month of the year. These month codes are used for all years with two exceptions. In a leap year, the month code for January is 5 and for February it is 1. The month codes with the corresponding mnemonics are as follows:
January – 6 (WINTER has 6 letters)
February – 2 (second month)
March – 2 (2-foot marches)
April – 5 (APRIL has 5 letters)
May – 0 (MAY0 for mayonnaise)
June – 3 (JUN has 3 letters)
July 5 (JULIE has 5 letters)
August – 1 (August begins with an A, the first letter)
September – 4 (SEPT has 4 letters)
October – 6 (Halloween TRICKS or GIFTS have 6 letters each)
November – 2 (second last month)
December – 4 (CHRISTMAS has 4 letters)
Third, we assign a code number for each year. For example, the year code for 2011 is 6.
The formula
Day of the week = (Month code + Date + Year code) mod 7
Note: mod 7 indicates the remainder you get by dividing by 7.
Examples of
What is the day for July 16, 2011?
Day of the week = (Month code + Date + Year code) mod 7
Day of the week = (5 + 16 + 6) mod 7 = 27 mod 7 = 6 (So it’s Saturday)
What is the day for December 25, 2011?
Day of the week = (Month code + Date + Year code) mod 7
Day of the week = (4 + 25 + 6) mod 7 = 35 mod 7 = 0 (So it’s Sunday)
Hurrah! With constant practice, you are now ready to be the walking schedule. Amaze your friends, colleagues, students, teachers and everyone else.